/**
 * index.html的css样式表定义
 */
.node circle {
  cursor: pointer;
  fill: #fff;
  stroke: steelblue;
  stroke-width: 1.5px;
}
.node text {
  font-size: 11px;
}
path.link {
  fill: none;
  stroke: red;
  stroke-width: 1.5px;
}